1. Field of the Invention
This invention relates, in general, to pumping devices and more particularly to pumping devices with electrical relay means for relaying information from within an explosive environment to a remote location.
2. Description of the Prior Art.
In a pumping device for pumping flammable liquids it is often necessary to provide a relay means to a remote location. This relay means transfers information such as the quantity of liquid that has been pumped. One example of this type of device is found in a gasoline service station. Here, a gasoline pump located in an open parking area transfers gasoline to vehicles. However, it is often desired or necessary that the information as to the quantity of gasoline pumped be relayed to a building where an attendant can record it and collect the proper fee. One of the most efficient means for transferring this information is by an electrical wire. The problem with this electrical means of transferring the information is the explosive environment around the pumping device.
Inside the gasoline pump housing, gasoline fumes can accumulate creating an explosive environment. All electrical devices within the explosive environment must, therefore, be explosion proof. One way to make electrical devices explosion proof is to adequately insulate them from the explosive environment. Thus, the main electrical supply to the pump is contained in an electrical make-up box which is insulated to keep out the explosive fumes.
Prior to this invention, electrical means for relaying the information as to how much gasoline had been pumped were made explosion proof by insulation. A magnet was connected to a shaft which rotated according to the quantity of gasoline being pumped. A glass container with wires sealed inside sensed the rotating magnet. This sensing was accomplished by two closely spaced bare wires which were brought into contact as the magnet passed closely by. The pulse produced was relayed to a remote location. To operate, this device required a high current. Therefore, all of the connections and wires were specially protected to prevent a short circuit and an explosive spark. This type of device, while performing adequately, is subject to improvement.
It is accordingly an object of the present invention to provide a safer and less expensive relay means.